The present invention relates to a method of measurements and control of geometrical parameters of microobjects having a trapezoidal shape. It can be used in a microelectronics technology for controlling the results of one of the main technological operations, namely photolithography.
Modern microelectronics technology applies high requirements to the quality of a photoresist mask which is formed by photolithography, as well as electron-beam and x-ray lithography. In particular side faces of the formed shaped elements of resistive mask must be close to vertical as much as possible, so as to guarantee a high reproducability of subsequent processes of chemical, plasma-chemical, ion-beam or another method of etching of technological layers of microcircuit to be formed through the above mentioned photoresist mask. However, in view of various reasons, technically it is not possible to produce details of the photoresist mask with exactly vertical side faces. As a result, the shaped details of the photoresist mask formed in a lithographic process have a typical trapezoidal shape in a cross-section. Conventionally, an angle of inclination of the side face is different from 90xc2x0 by a few degrees, depending on the type of the used photoresist and the technology of exposure and development of the resistive layer. Special regulations require that by the year 2012 the angle of inclination of the side face of details of the photoresist mask in the microelectronic technology must not be less than 88xc2x0. Therefore, the angle of inclination of the side face in the microelectronic industry is a very important parameter to be controlled, in accordance with which sorting out of inadequate microelectronic products at different stages of its manufacture is performed.
It is known to control the geometric shape of the shaped parts formed on a flat surface, including an angle of inclination of the side face of photoresist mask, by direct measurements of the angle on a film of a cross-section of the microelectronic structure obtained in an electron microscope. This method has many disadvantages. First of all the measurement of the angle of inclination of the side face is performed in two steps which are spaced from one another in time and space: preparation of a cross-section and its subsequent measurement by means of a microscope. The first step usually is performed in accordance with a special technology outside of the measuring microscope and is accompanied by an irreversible destruction of the object of measurement. The second step is characterized by a low efficiency, since it is necessary to introduce the prepared cross-section into a microscope chamber and provide, its positioning, focusing of an image, its fixation, and processing for obtaining values of the angle of inclination.
Accordingly, it is an object of the present invention to provide a method of measuring an angle of inclination of trapezoidal microobject side faces, which avoids the disadvantages of the prior art.
More particularly, it is an object of present invention to provide a method of measuring an angle of inclination of trapezoidal microobject side faces, in accordance with which it is not necessary to destroy an object of measurement during a standard procedure, namely measurement of linear sizes in a scanning electron microscope, with a process performed at the same time and in the same space.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a method measuring an angle of inclination of trapezoidal microobject side faces, which includes positioning an object in a microscope so that a direction along which a scanning of a video signal is to be performed is substantially perpendicular to an orientation of a n inclined side face, determining on a video signal two main peaks near edges of an object to be measured which are edge peaks having an asymmetrical shape, in each left and right edge peaks of the video signal, analyzing a left edge peak and a right edge peak of the video signal with the use of two spaced points on each edge, and determining an angle of inclination of a side face, based on the analysis of the left and right edge peaks of the video signal.
When the method is performed in accordance with the present invention, it eliminates the disadvantages of the prior art and provides for the above mentioned highly advantageous results.